Electronic dance music (EDM) DJs are not well-known in the US. Only a tiny portion of the population listens to EDM. I'm 29 and have friends that are very interested in EDM and I've never heard of Armin van Buuren either, but have heard of Linkin Park (of course I was directly in the middle of their demographic when they broke out). I suspect this is a regional issue. In the US the marketing value of having <insert any known US band here>'s DJ is probably higher than having Armin van Buuren if you are trying to target a broad demographic out of the gate and not going for the hardcore early adopter strategy.